<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <script>
        function text(){
        let a = prompt("输入银行卡余额");
        let b = prompt("输入当月食宿消费金额");
        let c = prompt("输入生活消费金额");
        let d = a-b-c;
        return d;
}
    let money = text();
    document.write(money);
    </script>
</body>
</html>